misfire

[rallyaddict]

1999 Cavalier Z-24 2.4L 5spd

This engine has a very bad misfire. Usually just before the temp gauge hits 90. At least 2 cyl are misfiring and it happens repeatidly until I let off the throttle. Sometimes car will stall. Usually just shakes very badly. No power at all. If I apply and let off throttle a few times problem goes away.

Car will drive perfectly afterwards until engine cools down again. Sometime check engine light comes on but it will go off on it's own.

I've had it to GM for service

Garage 1:

engine diagnostic: general misfire
reprogrammed PCM
repalced fuel filter

Garage 2:

engine diagnostic: cyl #3 misfire
cleaned fuel injectors

What I've done:

Checked for vacuum leaks (incl around throttle body)
Changed spark plugs (AC Delco platinums)
Checked spark plug boots
Cleaned throttle body & checked bolts (while I had the intake off)
Measured primary & secondary coil resistance
Checked IAT sensor and harness (ran out of time to check other sensors)
Checked all connectors
Checked grounds

I would greatly appreciate some insight wrt this problem.

I'm thinking this problem is occuring when the PCM goes into closed loop.
I would appreciate info on what exactly the PCM is looking for as soon as it goes into closed loop.

Thanks in advance

[rallyaddict]

It's gotten worse now. There's no particular time it will freak out. It may stall warming up then drive 40 miles without a misfire. OR it could misfire for 20 miles.

Crazy.

[public]

Sound like a bad coil to me. The coil-pak's can develop small cracks that only open up when hot, this will cause the problem you describe.

[rallyaddict]

Originally Posted by public

Sound like a bad coil to me. The coil-pak's can develop small cracks that only open up when hot, this will cause the problem you describe.

So should I be able to determine this if I check the coil resistance with warm engine then?

[public]

Not always. The multi-meter does not use enough voltage to "hop" thru the crack. Some shops can test these. Call around.

[rallyaddict]

Originally Posted by public

Not always. The multi-meter does not use enough voltage to "hop" thru the crack. Some shops can test these. Call around.

Thanks for the help. I think your diagnosis seems dead-on, based on the info I posted. I was convinced that's what it was.

One key point I realized (and failed to mention) is that the tach needle goes CRAZY during the event. It's not a slight jump or dive. The needle will go right to 0 or 1000 maybe 4 times within maybe 3 seconds while along the highway. Once the misfire event passes the tach is back to normal.

So since the engine is not really turning at the values the tach is telling me (during the misfire), I'm thinking the problem may be with the crankshaft position sensor circuit.

[public]

Originally Posted by rallyaddict

Thanks for the help. I think your diagnosis seems dead-on, based on the info I posted. I was convinced that's what it was.

One key point I realized (and failed to mention) is that the tach needle goes CRAZY during the event. It's not a slight jump or dive. The needle will go right to 0 or 1000 maybe 4 times within maybe 3 seconds while along the highway. Once the misfire event passes the tach is back to normal.

So since the engine is not really turning at the values the tach is telling me (during the misfire), I'm thinking the problem may be with the crankshaft position sensor circuit.

That is a possability. These don't fail often, but they do. These are a little hard to get to. Only one bolt and No way to test that I am aware of.

[big dude1]

so true so true...

[rallyaddict]

IT'S BACK!

After my last post the car ran like a top.
The temps were well below freezing.

Today it was around freezing or slightly above & it came back with a vengance.


The other thing I did was fill the tank with gas. I find the pumps at the garage I go to kick out before the tank is full, so I fill it slowly to the top.

Could a problem occur if it was filled up to the neck?

[noshun]

Originally Posted by rallyaddict

IT'S BACK!

After my last post the car ran like a top.
The temps were well below freezing.

Today it was around freezing or slightly above & it came back with a vengance.


The other thing I did was fill the tank with gas. I find the pumps at the garage I go to kick out before the tank is full, so I fill it slowly to the top.

Could a problem occur if it was filled up to the neck?

Yes the cap may not be able to relieve the vaccuum made by the tank emptying and it could even cause the tank to suck itself in! Just undo it after a short while if you're going to do that.

[rallyaddict]

Originally Posted by noshun

Yes the cap may not be able to relieve the vaccuum made by the tank emptying and it could even cause the tank to suck itself in! Just undo it after a short while if you're going to do that.

Thanks for the reply.
I'll check that.

I noticed your quote.
I went to Wales rally GB last year. Stayed at a friends place outside Bristol. The narrow country roads were amazing. Esp the overgrown ones where it's like driving through a tunnel. That was an experience on it's own.

[noshun]

Originally Posted by rallyaddict

Thanks for the reply.
I'll check that.

I noticed your quote.
I went to Wales rally GB last year. Stayed at a friends place outside Bristol. The narrow country roads were amazing. Esp the overgrown ones where it's like driving through a tunnel. That was an experience on it's own.

Yeah wales is pretty good for driving! I don't think WRC is going back to the UK though as the police suck dick when it comes to speeding, they had a blitz on the drivers travelling from satge to stage and the drivers just though, it's ok I'm leaving the county (non-british that is) but the british Police hunted them all down and fined the shit out of them! This kind of thing is why I left England, my native land for Canada! I love it here although there are few bendy roads. If you can try get to the isle of Man one day. The driving roads there are a Tarmac Rally all over the isalnd and get this! No BS! No speed limilts!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Anywhre on the island. You can still get busted for dangerous driving though! I'd live there if they didn't have so many F*cked up laws! Can't think of any examples but they are extremely weird!!!!! Oh yeah lots of camber changes and air giving crests on Isle of man roads, Well anywhere in England really! I used to have a loop that was about 10 miles long I used to burn around. One spot i'd get air, there were about 7 90 degree ebns, adverse camber, countless crests etc. So much fun! All made all the more intense when it's about 1 and a 1/4 cars wide, a 2 way road and you're doing 85-90 mph along it!!! I used to love scaring the sh*t out of people!!!! You watch the Fomrer SCCA Pro-Rally now Rally America? I can't believe the FWD SRT-4 (i know they all are but just to highlight this) Consistent top 5 finishes OVERALL!!! Faster then group N imprezas and Evos and only a few seconds off the Open class subes and Evos! MESSED up!!

[rallyaddict]

Originally Posted by noshun

Yeah wales is pretty good for driving! I don't think WRC is going back to the UK though as the police suck dick when it comes to speeding, they had a blitz on the drivers travelling from satge to stage and the drivers just though, it's ok I'm leaving the county (non-british that is) but the british Police hunted them all down and fined the shit out of them! This kind of thing is why I left England, my native land for Canada! I love it here although there are few bendy roads. If you can try get to the isle of Man one day. The driving roads there are a Tarmac Rally all over the isalnd and get this! No BS! No speed limilts!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Anywhre on the island. You can still get busted for dangerous driving though! I'd live there if they didn't have so many F*cked up laws! Can't think of any examples but they are extremely weird!!!!! Oh yeah lots of camber changes and air giving crests on Isle of man roads, Well anywhere in England really! I used to have a loop that was about 10 miles long I used to burn around. One spot i'd get air, there were about 7 90 degree ebns, adverse camber, countless crests etc. So much fun! All made all the more intense when it's about 1 and a 1/4 cars wide, a 2 way road and you're doing 85-90 mph along it!!! I used to love scaring the sh*t out of people!!!! You watch the Fomrer SCCA Pro-Rally now Rally America? I can't believe the FWD SRT-4 (i know they all are but just to highlight this) Consistent top 5 finishes OVERALL!!! Faster then group N imprezas and Evos and only a few seconds off the Open class subes and Evos! MESSED up!!

Yeah, they're pretty tough on speeding. We were on our best behavior but still managed to our picture taken in Cardiff compliments of a traffic camera. As for odd laws there is definatly some differences. I like the part about open liquour in the vehicle, but I don't like the part about strict speed enforcement.

I've heard stories very similar to the one you mentioned. I couldn't get over the windy roads and scenery as well. I've learned mini roundabouts can make a good chicane & I was told it's not uncommon for mirrors of opposing vehicles to "click" each other at speed.

As for Rally America, I have not seen any coverage. I've been trying to find out when, or if it will be broadcast. I'm waiting patiently for the Canadian Rally Championship TV coverage. As for WRC, rally Sweden will be on speed channel tomorrow night.

[noshun]

Originally Posted by rallyaddict

Yeah, they're pretty tough on speeding. We were on our best behavior but still managed to our picture taken in Cardiff compliments of a traffic camera. As for odd laws there is definatly some differences. I like the part about open liquour in the vehicle, but I don't like the part about strict speed enforcement.

I've heard stories very similar to the one you mentioned. I couldn't get over the windy roads and scenery as well. I've learned mini roundabouts can make a good chicane & I was told it's not uncommon for mirrors of opposing vehicles to "click" each other at speed.

As for Rally America, I have not seen any coverage. I've been trying to find out when, or if it will be broadcast. I'm waiting patiently for the Canadian Rally Championship TV coverage. As for WRC, rally Sweden will be on speed channel tomorrow night.

Didn't realise until just read your profile that you are in N.S. Rally America comes into Canada for a few legs during the season it's not easy to follow mind. There should be info on www.rally-america.com. Iwas going to Join the Ontario Rally Association and every year they have Navigatio rally's on public roads with checkpoints and such and always wanted to enter but I thought I wouldn't want to do proper rallying in a road car as it's a little tough on a car and Circuit racing is a little easier on the car, and a LOT more predictable! Although I went to a rally school and thrashed everyone! The instructor guy was amazed as everyone was slowing for this corner so they could get traction out and I was turning in, giving it gas for oversteer and then short shifting as it was on Mud! I was cutting laps about 2 seconds better then anyone else on one sorner doing what I thought was best, then I did what the instructor said the last time and hit a little understeer but was getting ready to unleash the secret weapon, Left foot braking and the Penis grabs the handbrake and we slide side-ways! Even with the off I come in only 2 seconds down! He ruined my day! That was in English Mk2 Ecort RS2000s! They were rally gods until the Audi Quattro Made mincemeat out of everything! Ever caught the pikes peak hill climb. I watched Didier Auriol (Video) do this in a Special pikes peak Pegeout 405 and most tof the way he was steering one handed with the other hand blocking the sun from his eyes!!! It was the fastest time yet at the point. Early nineties though!

[rallyaddict]

Originally Posted by noshun

Didn't realise until just read your profile that you are in N.S. Rally America comes into Canada for a few legs during the season it's not easy to follow mind. There should be info on www.rally-america.com. Iwas going to Join the Ontario Rally Association and every year they have Navigatio rally's on public roads with checkpoints and such and always wanted to enter but I thought I wouldn't want to do proper rallying in a road car as it's a little tough on a car and Circuit racing is a little easier on the car, and a LOT more predictable! Although I went to a rally school and thrashed everyone! The instructor guy was amazed as everyone was slowing for this corner so they could get traction out and I was turning in, giving it gas for oversteer and then short shifting as it was on Mud! I was cutting laps about 2 seconds better then anyone else on one sorner doing what I thought was best, then I did what the instructor said the last time and hit a little understeer but was getting ready to unleash the secret weapon, Left foot braking and the Penis grabs the handbrake and we slide side-ways! Even with the off I come in only 2 seconds down! He ruined my day! That was in English Mk2 Ecort RS2000s! They were rally gods until the Audi Quattro Made mincemeat out of everything! Ever caught the pikes peak hill climb. I watched Didier Auriol (Video) do this in a Special pikes peak Pegeout 405 and most tof the way he was steering one handed with the other hand blocking the sun from his eyes!!! It was the fastest time yet at the point. Early nineties though!

I saw a similar (or maybe the same) video. Climbdance. It's worth the download. This has Ari Vatanen is driving.

http://www.geocities.com/nosro/climbdance/

Here is a clip of Gigi I'm sure you'll enjoy.

http://www.allmotorlink.com/galli_video/gigi_6.wmv